The purpose of the proposed research is to examine in detail the neural basis of excitation and inhibition generated in the Pavlovian conditioning of cats by the use of a threshold probe technique. The threshold probe technique consists of pairing a conditioned stimulus (CS) with threshold electrical stimulation of the brain. The effect of the CSs upon the stimulation threshold provides an index of excitability of the particular structure. A decrease in the threshold reflects an excitatory process whereas an increase in the threshold reflects an inhibitory effect. It is planned to condition animals using stimulation of one brain site as the unconditioned stimulus and to use the threshold tests in this and other brain areas in order to delineate a system of structures mediating the acquisition of particular kinds of behavior such as defense or flight in the cat. In addition the role of the septal area in mediating the inhibition will be determined by cholinergic blockade of the septum. It is also planned to look at septal inhibition in other kinds of experimental paradigms such as learned helplessness and experimental neurosis. Finally, the motivational consequences of septal inhibition will be examined.